It is difficult to place and support a post, pole or other like slender object (referred to herein collectively as a "post" for ease of reference) into certain types of ground or soil conditions. Particularly problematic are the loose or "cohesion-less" soils, such as sand or loose aggregate, as well as ground with a high liquid content, such as swamps, peat bogs and marshes. In such ground conditions problems arise with insertion of the post into the ground and inadequate support for the post upon insertion. Post-receiving holes dug in sandy soils tend to collapse into themselves, requiring the removal of large volumes of soil to achieve a desired depth of hole, which soil must then be replaced about the post upon insertion. Opening a post-receiving hole in marshy conditions is typically impossible because of the fluidity of the material. Another drawback in such ground conditions are the additional supports that must often be provided to hold the post upright upon insertion.
The above noted problems are often encountered with the installation of utility posts in northern Canada in the large tracts of marshy land known as "muskegs", shown in FIG. 1. A muskeg typically has a top layer 16 (commonly a foot to several feet deep) of firm decomposed organic matter that "floats" on a marshy material 17 (up to 30 feet deep) which itself sits over an impermeable base such as clay. The vertical post 10 can not be supported by the relatively soft organic top layer 16 nor the marshy material 17 alone, and either the post is too short for insertion into the relatively firm clay base or it would be impractical to do so. Hence, a "ship's mast" method of supporting the vertical post is typically used where the post is sunk about six feet into the muskeg and a pole 12 is bolted generally perpendicularly to the post 10 at ground level to act as a base. Guy wires 14 are attached from the ends of the base pole 12 to the vertical post 10 to prevent the post from tipping in a transverse direction (i.e. in the plane formed by post 10 and pole 12). The resulting ship's mast structure is difficult, cumbersome, awkward and time consuming to construct and set up. It also does not support the vertical post in a direction transverse to the base pole 12 prior to installation of utility wires on the post, and therefore the post is prone to tipping over until such wires are installed. Another recurrent problem is ground instability or shifting due to freeze/thaw cycles, during which the post 10 tends to shift, lean or fall since it is not anchored in a firm base. Hence, the ship's mast structure has significant drawbacks and is not very reliable, even though it is a popular mode of post support in muskegs.
Some prior patents, such as U.S. Pat. No. 5,066,168 (Holdeman) and U.S. Pat. No. 4,621,950 (Kinnan), disclose foundation devices for supporting posts, but which are not adapted for use in muskeg type of conditions and suffer from some of the following disadvantages. First, none of the prior devices are adapted for use both with and without an auger device for ground penetration, and therefore are not suitable for use in certain ground conditions. Second, the devices are not modularized, namely their lengths are fixed and can not be extended on-site to accommodate changing ground conditions. Length extendibility is desirable particularly in areas where the depth of suitable ground support strata is not known in advance and may be greater than expected. Simply manufacturing the prior art foundation devices longer is not feasible due to increased costs and wastage of material, and greater transportation and handling difficulties. Third, the prior devices employ a system of bolted plates at their top ends for transferring rotative drive from a drive machine to the device. These plate systems, although effective in transferring drive force, do not provide an easy and quick means of coupling/uncoupling the drive and the support device for enhanced installation efficiency. Further, the coupling plates obstruct or prevent escape of soil from within the support devices, which can hamper or prevent proper installation of the foundation device, particularly where the top of the foundation device must end up at or near ground level.
What is therefore desired is a novel device for supporting posts in muskegs and other like difficult ground support conditions, and which overcomes the limitations and disadvantages of prior support devices. Preferably it should provide for simple, quick and reliable coupling of the support device with any rotative drive means, and avoid obstructing any egress of ground material from within the support device during installation, nor manual removal of ground material thereafter for the subsequent insertion of a post therein. The support device should be suitable for use with or without an auger. Furthermore, the device should be capable of length variation, namely by coupling modular sections for length extension.